I’ve finally got around to cycle my tank and have taken a GH & KH test for the first time. The GH reading is off the API scale. The scale stops at 12 drops of solution which equals 200-400ppm, it took 16 drops for my sample to change colour.

Do I need to do anything or will the fish I finally purchase adjust to this high reading?

Looking at those stats you’re in a hard water area, which is better suited to fish like livebearers, rainbows or Rift Lake cichlids.

However a 35L tank isn’t big enough for most of those options. I note that you’re considering guppies, so a male-only group of five or maybe six would work well. Most of the suggestions in the other thread are of softwater fish, which you could keep if they were locally bred but would fare better if the water was softened eg by using a reverse osmosis unit.

Softening water using “pillows” or some such is pretty difficult and most likely entrirely inefficient – the only method that would truly soften [1] the water is if the pilliow contains a ion-absorbing compound (to JUST soften the water, and not affect other chemical aspects of the water, that gets a bit too complicated for this post, it should ONLY absorb Calcium and Carbonate ions).

An RO unit will remove ions from the water by passing the pure water through a little “sieve” that prevents most other things from getting through. It does have a few drawbacks: 1. It produces about 80% waste-water and 20% “clean” water. The waste-water can be used for keeping “hard-water tolerant fish”, or used to water the plants, but many people just drain it into the waste-drain.

2. It requires good pressure from the water-supply to produce the advertised amount of water. This is probably not a real problem to you, as your tank is fairly small.

3. Pure water is inherently unstable. You need to mix tap-water or add KH buffering capacity (such as Sodium Bicarbonate just like the stuff used for baking and such – not baking powder, tho’, as it has other compounds mixed in).

4. The RO unit needs costs money – both initial purchase and running costs in replacement carbon and particle filters. And of course, if you pay for the water itself, you need to pay for more water.

There are quite a few fish (particularly the ones commonly sold in the LFS) that are tolerant to a rather wide variation in hardness. Whilst I agree that the above suggested fish are ideal for the hardness you have, there is no reason to go to extremes to keep most commonly available South American or Asian fish in hard water, unless you start looking for specialized soft-water species – I wouldn’t put Ancistrus dolichopterus (starlight bristlenose) in hard water for example. But common Bristlenose would work just fine, for example. This means that for example a house-water-softener is completely useless for removing hardness for aquarium use – it simply converts calcium ions and carbonate ions into sodium (or potassium) and chloride ions – so instead of hard water, we have just lightly salted water… Which is just as bad for soft-water loving fishes…

[1] In my opinion, hardness as such isn’t particularly important. It is, however, important to understand the ion-content in the water, which is normally measured as conductivity – the water’s ability to transfer electricity – more ions, more conductivity. You can buy a $30/£20 instrument that measures either electrical conductivity (EC) or “Total Dissolved Solids” (TDS) in parts per million (or mg/l). The instrument is exactly the same thing, just different scales – TDS is about half the EC number. For most intents and purposes, it doesn’t really matter if this is calcium, magnesium, sodium or potassium or any other ions. Only calcium and magnesium is counted as hardness.

Most “mineral water” is quite hard. Some bottled water in shops is quite soft, and that can be used for aquarium purposes. But most things called “mineral water” contains quite a bit of minerals [it would be false marketing if it didn’t, right?].

Most bottled water has labels telling you how much of what the water contains. The bits to look for when it comes to hardness is Magnesium and Calcium Mg2+/Ca2+ ions. If that number is high (meaning more than 30-40 mg/l), then it’s not suitable for soft water use in an aquarium. There is usually also a “solids at 180’C” or some such, that tell you the overall TDS value (sort of, since the 180’C means that the carbonate has disassociated into carbon dioxide and oxide). If this value is more than about 100mg/l, again, it’s unlikely to be good for making soft aquarium water.

My suggestion would echo Eyrie’s advice. As a beginner you might do better to keep the fish suited for your water, then as you progress as a hobbyist with a little experience you could move onto experimenting with your water /biggrin.gif” style=”vertical-align:middle” emoid=”:D” border=”0″ alt=”biggrin.gif” /> You may then think of going with a more conventionally shaped tank, as most fish prefer a linear swimming motion, as opposed to the vertical option that seems forced as a result of the shape of the Bi-ube

Fair enough /smile.gif” style=”vertical-align:middle” emoid=”:)” border=”0″ alt=”smile.gif” /> Your only real option is RO water reconstituted either by mixing in your tap water, or with some sort of remineralisation product like Tropic Marin Pro Discus. Attempting to adjust your tap water with a softening product will most likely end in failure, and some expense.

I’ve already done a 25% water change with mineral water as it fitted within the parameters MatP mentioned earlier. It brought the GH down to 214.8ppm from 304.3ppm which is quite significant. I’ll just need to make sure it hasn’t caused problems elsewhere (ph, KH, ect.).

Before you start tampering with the water ask yourself this question, is this something I have the time and energy to do each week?

The most important thing in an aquarium is to keep things stable. Many of the fish bred for commercial purposes from Germany are used to quite hard water even though they are soft water species.

Unless you want to breed the fish or have sensitive fish don´t tamper to much with water. And hard water is more stable with regards to pH fluctuations s it might actually be a good thing considering you´re just starting out.